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Improved rapid anaerobic treatability/toxicity screening procedure

page 115

Section Four
BIOLOGICAL:
BIODEGRADATION AND TREATABILITY
13 IMPROVED RAPID ANAEROBIC
TREATABILITY/TOXICITY SCREENING PROCEDURE
Thomas R. Wynn and Enos L. Stover
The Stover Group
P.O. Box 2056
Stillwater, Oklahoma 74076
John N. Veenstra, Professor
School of Civil and Environmental Engineering
Oklahoma State University, Stillwater, Oklahoma 74078
ABSTRACT
An experimental procedure was developed by Brooks et al.1 for anaerobic screening studies
using 125 mL syringes with luer-lock valves. This procedure was performed under static conditions with intermittent mixing twice per day. The new modified procedure involves continuous
mixing on a shaker table. A specific test protocol has been developed with standardized operating conditions, including organic loads and volatile suspended solids concentrations. Advantages
of this procedure are reduction in test duration and minimal variability.
INTRODUCTION
Anaerobic treatment of municipal and industrial waste has been used with great success in stabilizing organic waste. The popularity of anaerobic treatment has risen in recent years, mostly
due to the high energy yielding by-product, methane. Other advantages include lower sludge
yields and treatment of high strength organic waste streams more economically than aerobic systems. Anaerobic treatment involves the decomposition of waste in the absence of dissolved oxygen and consists of sequences of reactions in which one group of microorganisms produces substrate for another group of microorganisms. The synergistic relationship produces a delicately
balanced environment which can diminish rapidly if environmental conditions are not satisfied.
Anaerobic treatability/toxicity screening tests provide needed information to maintain favorable
environmental conditions.
Anaerobic treatability/toxicity screening tests are bench-scale tests that simulate full-scale responses to waste streams. Information from these tests will determine the anaerobic treatability
and waste characteristics of a particular waste stream and can assist in developing large-scale
treatability studies. Types of treatability/screening tests include batch, continuous or semicontin-
uous feed assays. Each type of assay has advantages and disadvantages, with the ultimate selection depending on the desired information. Batch assays are quick, inexpensive, reproducible,
and tend to produce a conservative value for a toxicity evaluation.2 Inhibition and toxicity can be
evaluated from total volume and rate of gas produced. Gas production relates to the health of the
inoculum and a decrease in the rate or total gas produced indicates a negative effect from the
waste sample.3 Accurate gas measurements are essential when gas production is measured for indication of toxicity or inhibition.
A recent study by Brooks et al.1 evaluated the use of 125 mL glass luer-lock syringes for developing an anaerobic screening procedure. The glass luer-lock syringe was the reactor vessel
52nd Purdue Industrial Waste Conference Proceedings. 1997. Ann Arbor Press, Chelsea, Michigan 48118. Printed in
U.S.A.
115

Section Four
BIOLOGICAL:
BIODEGRADATION AND TREATABILITY
13 IMPROVED RAPID ANAEROBIC
TREATABILITY/TOXICITY SCREENING PROCEDURE
Thomas R. Wynn and Enos L. Stover
The Stover Group
P.O. Box 2056
Stillwater, Oklahoma 74076
John N. Veenstra, Professor
School of Civil and Environmental Engineering
Oklahoma State University, Stillwater, Oklahoma 74078
ABSTRACT
An experimental procedure was developed by Brooks et al.1 for anaerobic screening studies
using 125 mL syringes with luer-lock valves. This procedure was performed under static conditions with intermittent mixing twice per day. The new modified procedure involves continuous
mixing on a shaker table. A specific test protocol has been developed with standardized operating conditions, including organic loads and volatile suspended solids concentrations. Advantages
of this procedure are reduction in test duration and minimal variability.
INTRODUCTION
Anaerobic treatment of municipal and industrial waste has been used with great success in stabilizing organic waste. The popularity of anaerobic treatment has risen in recent years, mostly
due to the high energy yielding by-product, methane. Other advantages include lower sludge
yields and treatment of high strength organic waste streams more economically than aerobic systems. Anaerobic treatment involves the decomposition of waste in the absence of dissolved oxygen and consists of sequences of reactions in which one group of microorganisms produces substrate for another group of microorganisms. The synergistic relationship produces a delicately
balanced environment which can diminish rapidly if environmental conditions are not satisfied.
Anaerobic treatability/toxicity screening tests provide needed information to maintain favorable
environmental conditions.
Anaerobic treatability/toxicity screening tests are bench-scale tests that simulate full-scale responses to waste streams. Information from these tests will determine the anaerobic treatability
and waste characteristics of a particular waste stream and can assist in developing large-scale
treatability studies. Types of treatability/screening tests include batch, continuous or semicontin-
uous feed assays. Each type of assay has advantages and disadvantages, with the ultimate selection depending on the desired information. Batch assays are quick, inexpensive, reproducible,
and tend to produce a conservative value for a toxicity evaluation.2 Inhibition and toxicity can be
evaluated from total volume and rate of gas produced. Gas production relates to the health of the
inoculum and a decrease in the rate or total gas produced indicates a negative effect from the
waste sample.3 Accurate gas measurements are essential when gas production is measured for indication of toxicity or inhibition.
A recent study by Brooks et al.1 evaluated the use of 125 mL glass luer-lock syringes for developing an anaerobic screening procedure. The glass luer-lock syringe was the reactor vessel
52nd Purdue Industrial Waste Conference Proceedings. 1997. Ann Arbor Press, Chelsea, Michigan 48118. Printed in
U.S.A.
115